import pygame
from pygame.sprite import Sprite

class Bullet(Sprite):
    def __init__(self, ai_game):
        super().__init__()
        self.screen = ai_game.screen
        self.settings = ai_game.settings
        self.color = self.settings.bullet_color

        # (0,0)处创建子弹再设置到飞船的中间顶部
        self.rect = pygame.Rect(0, 0, self.settings.bullet_width, self.settings.bullet_height)
        # 子弹初始位置在飞船顶部中间
        self.rect.midtop = ai_game.ship.rect.midtop
        # 获取子弹y坐标轴上的数值
        self.y = float(self.rect.y)

    # 子弹向上移动
    def update(self):
        self.y -= self.settings.bullet_speed
        self.rect.y = self.y

    # 将子弹绘制到屏幕上
    def draw_bullet(self):
        pygame.draw.rect(self.screen, self.color, self.rect)
        